Electric volume control



Filed July 10, 1945 Fig.4

WITNESSES: INVENTOR 7%. 0 V 4. WM, 7 WW6 4 ATTORISEYQ Patented Mar. 22, 1949 ELECTRIC VOLUME CONTROL Henry M. Dressel, St. Marys, Pa., assignor to Stackpolc Carbon Company, St. Marys, Pa., a corporation of Pennsylvania Application July 10, 1945, Serial No. 604,206

(01. fill-55) 6 Claims.

This invention relates to variable resistance units, and more particularly to miniature volume controls for radios.

In miniature volume controls there can be very little room for the necessary elements, so the elements are made as small and few in number as possible. One such miniature volume control is shown in Hathorn Patent No. 2,160,142. In that control a contact member, which slidably engages a resistance element, extends loosely through a head on the end of a control shaft. Attached to the opposite side of the head is a flat spring conductor the ends of which slidably engage the end wall of the metal housing that encloses the head and resistor and that forms part of the electric circuit. Between its ends this conductor engages the contact member and presses it against the resistance element. Such a unit functions satisfactorily, but in some cases its life is relatively short because when a spring conductor is used which is stiif enough to engage the housing and contact with the desired pressure, it may press the contact against the resistance element so heavily that the contact will wear away the element.

It is among the objects of this invention to provide a volume control which is very small, which has a long life, which is inexpensive, and which is simple to construct.

In accordance with this invention a control shaft extends through the center of a base member and into a metal housing in which there is an arcuate resistance element. The resistance element and the housing are adapted to be connected into an electric circuit. A head is rigidly mounted on the inner end of the shaft and carries a, contact member in sliding engagement with the resistance element. The contact memher most suitably is a flat spring type of contact rigidly connected to the head. The head also carries a resilient electric conductor which is in sliding engagement with the side wall of the housing and is electrically connected to the contact member. As this conductor does not have to press the contact against the resistance element, the conductor can be made stiii enough to engage the housing with the desired amount of pressure without affecting the life of the resistor. Preferably, the conductor is in the form of a resilient wire rigidly connected to the head and projecting laterally from it into engagement with the side wall of the housing.

The preferred embodiment of the invention is illustrated in the accompanying drawings in which Fig. 1 is a perspective View of my control unit; Fig. 2 is an enlarged plan view with the top .or end wall of the housing removed; Fig. 3 is a transverse section through the housing showing the elements inside in elevation; and Fig. 4 is a view similar to Fig. 3, but turned Referring to the drawings, an insulated base i of molded Bakelite or the like is provided with a central opening from the bottom of which a threaded metal bushing 22 extends. Mounted on top of the base is a cylindrical metal housing 3 that is held in place by integral lugs t bent under the base. This housing is provided with a laterally projecting terminal member 6 adapted to be connected in an electric circuit. A metal control shaft 2 extends through the bushing and base and up into the housing from the top of which it is spaced by a thin insulating disc 8 inside the housing. Upward movement of the shaft also is limited by a clamping ring 9 (Fig. 3) projecting from a peripheral groove in the shaft directly below the lower end of the bushing. The upper end of the shaft projecting above the base has a flattened portion on which a spacing washer ii and a disc-like head 52 of insulating material are clamped by a metal washer 13 (Fig. 2) held in place by the upset end of the shaft. Mounted on the base around the control shaft is a substantially circular resistance element is the adjacent ends of which are connected by rivets l6 through the base to metal terminal members ll that project laterally from the base for connecting the resistor in the circuit.

According to this invention a substantially U-shape contact member 20 of the flat spring type has its ends rigidly connected by rivets 2| to the bottom of control head l2 on opposite sides of the shaft. The central portion of the contact member is bowed downwardly into sliding contact with the resistance element which it engages with light spring pressure. To c0nnect this contact into the circuit, a resilient conductor 22 is mounted on top of the head to which it is rigidly connected by the rivets 2 l. Of course, the rivets also electrically connect the conductor with the contact that is spaced from the conductor by the head.

The conductor prefer-ably consists of a spring wire bent into general U-shape with its two ends projecting beyond rivets 2i and the side of the head and into sliding engagement with the cylindrical side wall of the metal housing. The end portions of the wire beyond the rivets are inclined toward each other and then are bent outwardly again. The ends at the edge of the head are provided with reverse bends so that curved surfaces engage the housing. The side wall of the housing presses these ends inwardly and toward each other, and they engage the housing with considerable pressure. Due to the fact that the conductor 22 engages the side wall of the housing instead of its topwall, the height of the housing can be reduced. Also, the conductor is positively connected to the contact member by rivets 2|, so there is better electrical connection between the two than when a spring conductor presses against a contact member.

According to the provisions of the patent statutes, I have explained the principle and construction of my invention and have illustrated and described what I now consider to represent its best embodiment. However, I desire to have it understood that, within the scope of the appended claims, th invention may be practiced otherwise than as specifically illustrated and described.

I claim:

1. In a miniature volume control, the combination with a base member provided with an axial opening, a metal housing projecting from one side of the base and having a cylindrical side wall, an arcuate resistance element mounted on the base inside the housing, a control shaft rotatably mounted in said opening and projecting into the housing, and a head rigidly mounted on the inner end of the shaft, of a contact member carried by the head in sliding engagement with the resistance element, and a resilient wire mounted substantially flat on the head and projecting laterally therefrom into sliding engagement with said side wall of the housing, said wire being electrically connected to said contact.

2. In a miniature volume control, the combination with a base member provided with an axial opening, a metal housing projecting from one side of the base and having a cylindrical side wall, an arcuate resistance element mounted on the base inside the housing, a control shaft rotatably mounted in said opening and projecting into the housing, and a head rigidly mounted on the inner end of the shaft, of a contact member carried by the head in sliding engagement with the resistance element, and a resilient wire loop mounted on the head with the ends of the loop turned inward to provide curved portions and projecting laterally therefrom into sliding engagement with said side wall of the housing, said loop being electrically connected to said contact.

3. In a miniature volume control, the combination with a base member provided with an axial opening, a metal housing projecting from one side of the base and having a cylindrical side wall, an arcuate resistance element mounted on the base inside the housing, a control shaft rotatably mounted in said opening and projecting into the housing, and a head rigidly mounted on the inner end of the shaft, of a flat spring contact member secured to the head and slidably engaging the resistance element, and a resilient wire secured to the head and projecting laterally therefrom into sliding engagement with said side wall of the housing, said contact and wire being electrically connected.

4. In a miniature volume control, the combination with a base member provided with an axial opening, a metal housing projecting from one side of the base and having a cylindrical side wall, an arcuate resistance element mounted on the base inside the housing, a control shaft rotatably mounted in said opening and projecting into the housing, and an insulating head rigidly mounted on the inner end of the shaft, of a spring contact member engaging the head and slidably engaging the resistance element, a resilient wire on the opposite side of the head, said wire being bent into the general shape of a U with its ends projecting laterally from the head into sliding engagement with said side wall of the housing, and a pair of rivets spaced from the ends of the Wire and passing through the head to connect the wire and contact member to the head and to each other.

5. In a miniature volume control, the combination with a base member provided with an axial opening, a metal housing projecting from one side of the base and having a cylindrical side wall, an arcuate resistance element mounted on the base inside the housing, a control shaft rotatably mounted in said opening and projecting into the housing, and an insulating head rigidly mounted on the inner end of the shaft, of a spring contact member engaging the head and slidably engaging the resistance element, a resilient wire on the opposite side of the head, said wire being bent into the general shape of a U with its ends disposed close to each other and doubled back on themselves, said ends projecting laterally from the head into sliding engagement with said side Wall of the housing, and a pair of metal fastening members spaced from the ends of the wire and passing through the head to connect the wire and contact member to the head and to each other.

6. In a miniature volume control, the combination with a base member provided with an axial opening, a metal housing projecting from one side of the base and having a cylindrical side wall, an arcuate resistance element mounted on the base inside the housing, a control shaft rotatably mounted in said opening and projecting into the housing, and an insulating head rigidly mounted on the inner end of the shaft, of a spring contact member engaging the head and slidably engaging the resistance element, a resilient wire on the opposite side of the head, said wire being bent into the general shape of a U with its ends disposed close to each other and doubled back on themselves, said ends projecting laterally from the head into sliding engagement with said side wall of the housing, diametrically opposite side portions of the wire being provided with radially extending reverse bends, and a pair of metal rivets extending through said bends and the head and contact member to connect them all together.

HENRY M. DRESSEL.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 2,160,142 Hathorn May 30, 1939 FOREIGN PATENTS Number Country Date 226,918 Great Britain Jan. 8, 1925 

